In this stuffy little room on the fifth floor of Burton Memorial Tower with a half-completed hangman scrawled jauntily on the blackboard, the Compulsive Lyres are making music.

It’s only their second time singing their newest song, “Sweet Caroline,” and it begins tentatively. The two beatboxers weave in and out of the melody like professionals, but something's missing. Maybe it’s because the chords are slightly out of sync, or that a section of the harmony sometimes seems to fade out, as if the singers aren’t quite sure of themselves.

Then, about a minute in, the chorus hits. As the chord progression swells up, the singers smile broadly at each other — this time, they know they’ve got it right. The sound that emerges this time is tonally and texturally lush, enveloping the group with its warmth.

From here, the energy bounces around the room like a ping-pong ball. By the second chorus, they are already into the groove of the song, snapping their fingers, joining hands and tapping their feet. “So good, so good, so good!” a singer cries out, using Neil Diamond’s words to authenticate the group’s exuberant performance.

Welcome to the crazy, doo-wopy, harmony-steeped world of a cappella.

From the hallowed history of Renaissance polyphony to contemporary barbershop quartets, a cappella, Italian for “in the manner of the church,” is a type of singing entirely unaccompanied by instruments and usually includes separate parts for each person.

But though it initially began as a style of religious music, a cappella is considerably more modern at the University – groups have been known to perform diverse selections from the likes of Michael Jackson to Lady Gaga to Hanson. Also innovative is some groups’ distinctive approaches to performance. Last year, the G-Men began sing-assaulting people on the Diag, in the Fishbowl and in the bathroom to publicize an upcoming concert — even performing a rousing rendition of “The Lion King” soundtrack on a University bus, roaring wildebeests and all.

The a cappella community at the University has fun, but don't be fooled — these groups are prestigious. Last February, the G-Men, Dicks & Janes and Amazin’ Blue competed against colleges across the Midwest in the International Championship of Collegiate A Cappella, an internationally recognized competition that attracts hundreds of college groups every year. All three ascended to the region’s semifinals, making Michigan the only school in the country to have that many groups at that level.

The process of choosing new singers begins at A Cappella Rush, an event put on by the Michigan A Cappella Council during the first week of the semester. Housed in the second floor Union Ballroom, rush typically consists of a small concert with one song performed by each of the 16 groups followed by a Q&A session. In a Festifall-style arrangement, different tables for each group are lined up around the perimeter of the stage, where curious students can roam around, ask questions and sign up for auditions.

“It’s a good way to get the flavor of all of them,” said Kat Weber, a second-year graduate student in the School of Public Health and member of the Compulsive Lyres.

“I didn’t really have a set idea about who I was going to audition for going in,” Maia Gleason an LSA freshman said. She tried out for four groups during September auditions: Amazin’ Blue, 58 Greene, Gimble and the all-girl Harmonettes, earning callbacks to three of them. She ultimately joined Gimble.

“For me, Gimble and 58 Greene really gave off that feel of fun — you know, it’s not always about the music,” she said. “It’s also about the passion, having fun with it and growing from the music you’re singing.”

Auditions run almost immediately after rush, over the course of three days. This year, the number of auditioners reached a record high, with as many as 150 students showing up per group.